#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int main()
{
	int i = 1, j = 1;
	double sum = 0.0;
	for (i = 1; i <= 100; i++)
	{
		sum = sum +j*1.0/i;
		j = -j;
	}
	printf("%lf", sum);
	return 0;
}